Towers of the kind mentioned above are commonly used in wind turbines for supporting a nacelle, including a generator driven by rotor blades, on a desired level above the ground or surface of the water in case of an offshore wind turbine. The tower comprises one or more tubular tower sections of steel having a circumferential jacket wall. The tower sections normally have a circular cross section but also other cross sectional shapes could be conceivable, such as an oval shape. Moreover, the tower can optionally be cylindrical or slightly truncated conical. Each tower section is formed with an inward directed flange in its lower and upper ends. In case the tower is composed of two or more tower sections, the sections are interconnected end to end by means of a bolt connection through the flanges. Also, the tower is mounted to a foundation by means of a bolt connection through the flange in the lower end of the lower tower section, and the nacelle is mounted to the tower by means of a bolt connection through the flange in the upper end of the upper tower section.
In a lower portion of the tower, a door is arranged through the jacket wall and inside the tower is provided with support structures and access equipment, such as platforms and ladders in order to allow access to the inner of the tower for maintenance and repairs of the inside of the tower and of the equipment inside the nacelle in top of the tower.
In prior art it is known to mount the platforms on the inside of the tower by means of bolting and/or welding to the jacket wall. For example by welding brackets to the inside jacket wall on which the platforms rest. The ladders are thereafter secured to the platforms. One disadvantage with such a solution is that the jacket wall will be weakened when the platforms are attached by bolting and/or welding, which might necessitate an increased material thickness in the jacket wall and hence increased costs. Another disadvantage is that this method of attaching platforms and ladders inside the tower, is not flexible in the sense that a possible adjustment or repositioning in the future will be very difficult. Such a rigid mounting may also affect the tower with unfavourable loads.
EP 1933029 discloses a method for mounting platforms and ladders inside a tower for a wind turbine. This method involves the use of beams, which are secured to the upper as well as the lower flange of each tower section. To the beams are, in its turn, mounted support structures such as platforms and ladders. The beams are attached to the upper flange in a rigid way by means of bolting or welding. The attachment to the lower flange, however, allows displacement of the beam in the longitudinal direction in relation to the flange, whereas the beam is fixed held in a direction perpendicular to its longitudinal direction in order to allow displacement of the beams, due to e.g. varying temperatures and deflection of the tower due to wind load, but ensure stability in the horizontal direction. The use of beams extending between the upper and lower flange of each tower section, is however a rather expensive solution for mounting equipment inside a tower and it is not as flexible as is desirable since the equipment are attached to the beams by means of e.g. bolting or welding, and as soon as any of the equipment are to be adjusted or repositioned, it is necessary to drill new holes in the beams or to make a new welding, which is time-consuming and elaborating.
It is also known in the art to attach an upper platform by means of rods from the upper flange of a tower section, such that the platform is suspended from the upper flange. A ladder is thereafter suspended from the platform and is stabilized by means of wires or the like, which are attached to the inside of the jacket wall by means of magnets. Such a solution has the advantage that it does not weaken the jacket wall. However, the possible alternatives for arranging equipment inside the tower section is very limited. Especially when it is desirable to arrange several platforms inside the same tower section.